Thanks for the heads up...I dont have a screen printer to really farm this out to. I have seen shirts with a photo on the shirt with a high gloss finish over the top to give it a overall rubbery feel but not sure what the process is to create such a shirt. I am going to try and get some more info before I have to pass but it looks like I am going that way.
I haven't ran across any plastisol transfer co that will produce halftones that will reproduce that look. It will take some graphic work and a better photo, nonetheless, to output a reasonable halftone for either direct screenprinting or transfer.
A DTG printer would work, but it would take a DTG capable of white ink on black. In addition the blanks are considerably more expensive.
I cant speak much for iron-ons, but some people have reasonable results with the inkjet papers for darks.
Long story short...direct screenprinting is your best option, that could be done with a 2, maybe 3 color simulated process print, white and 1-2 grays. If they are one-sided, you could get them for about $10 for 25, $8ish for 100 and maybe $6-7ish for 250.